Until we have one of our own, here's the intro from a Netcat tutorial I found:

Netcat is a utility that is able to write and read data across TCP and UDP network connections. If you are responsible for network or system security it essential that you understand the capabilities of Netcat. Netcat can be used as port scanner, a backdoor, a port redirector, a port listener and lots of other cool things too. It's not always the best tool for the job, but if I was stranded on an island, I'd take Netcat with me. During this tutorial I'll demonstrate a complete hack, using Netcat only, just to point out how versatile it is.